Okay, so I've got some video links for you, most of them cover how to harvest as well, and... some recipe links too!
Seems like the stuff that comes out of the mill is just chaff, according to this video:
There's also a simple video here:
Another to check out is (which says they have classes on how to make flour in a blender):
There's also a
Mesquite Video Resource Library with a few videos.
And last, but not least,
here's a place with mesquite flour recipes to try.
One more thing to note: aflatoxin can be an issue with mesquite, so you might want to make sure to prevent that as much as possible. That last site has a
PDF with aflatoxin in mesquite info. for their area and
here's the Wikipedia page on aflatoxin, which is a health concern in more than just mesquite. The PDF mentions testing for aflatoxin, but I'm not sure what's involved with that.